/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 2003-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: Utils.java,v 1.2.4.1 2005/09/15 08:15:30 suresh_emailid Exp $
 */
package com.sun.org.apache.xml.internal.serializer;

import java.util.Hashtable;

/**
 * This class contains utilities used by the serializer
 */
class Utils {

  /**
   * This nested class acts as a way to lazy load the hashtable
   * in a thread safe way.
   */
  static private class CacheHolder {

    static final Hashtable cache;

    static {
      cache = new Hashtable();
    }
  }

  /**
   * Load the class by name.
   *
   * This implementation, for performance reasons,
   * caches all classes loaded by name and
   * returns the cached Class object if it can previously
   * loaded classes that were load by name.  If not previously loaded
   * an attempt is made to load with Class.forName(classname)
   *
   * @param classname the name of the class to be loaded
   * @return the loaded class, never null. If the class could not be loaded a ClassNotFound
   * exception is thrown.
   * @throws ClassNotFoundException if the class was not loaded
   */
  static Class ClassForName(String classname) throws ClassNotFoundException {
    Class c;
    // the first time the next line runs will reference
    // CacheHolder, causing the class to load and create the
    // Hashtable.
    Object o = CacheHolder.cache.get(classname);
    if (o == null) {
      // class was not in the cache, so try to load it
      c = Class.forName(classname);
      // if the class is not found we will have thrown a
      // ClassNotFoundException on the statement above

      // if we get here c is not null
      CacheHolder.cache.put(classname, c);
    } else {
      c = (Class) o;
    }
    return c;
  }
}
